1. Field of the Invention
The present invention relates to an electron-beam apparatus, and an image forming apparatus, such as a display apparatus or the like, to which the electron-beam apparatus is applied. More particularly, the invention relates to a method for correcting beam deviation near a supporting member (a spacer) within an envelope.
2. Description of the Related Art
Two types of electron emitting elements, i.e., thermionic sources and cold-cathode electron sources, have been known. The cold-cathode electron sources include field-emission elements (hereinafter abbreviated as “FE elements”), metal-insulator-metal elements (hereinafter abbreviated as “MIM elements”), surface-conduction electron emitting elements (hereinafter abbreviates as “SCE elements”), and the like.
For example, the SCE elements have the feature that a large number of elements can be formed on a large area because of a simple structure and easiness of manufacture. For example, image forming apparatuses, such as image display apparatuses and image recording apparatuses, charged-beam sources, and the like are being studied as application fields of the SCE elements.
Particularly, as proposed, for example, in U.S. Pat. No. 5,066,883, and Japanese Patent Application Laid-Open (Kokai) Nos. 2-257551 (1990) and 4-28137 (1992) by the assignee of the present application, image display apparatuses obtained by combining SCE elements and phosphors emitting light by being irradiated by electron beams are being studied as application of SCE elements. Image display apparatuses of this type are expected to have characteristics superior to other conventional types of image display apparatuses. For example, image display apparatuses of this type are superior to recently diffused liquid-crystal display apparatuses in that a backlight is unnecessary because they emit light by themselves and the angle of view is wide.
In image display apparatuses of this type, spacer are usually disposed between a rear plate and a faceplate. A sufficient mechanical strength is required for the spacer in order to support the atmospheric pressure, and the spacer must not greatly influence the trajectory of electrons traveling between the rear plate and the faceplate. The factor for influencing the electron trajectory is charging of the spacer. The charging of the spacer is considered to be caused by incidence of part of electrons emitted from an electron source or electrons reflected by the faceplate onto the spacer followed by emission of secondary electrons from the spacer, or adherence of ions produced by collision of electrons to the surface of the spacer.
When the spacer is charged to a positive value, since electrons traveling near the spacer are attracted to the spacer, a displayed image is distorted near the spacer. The influence of charging is more pronounced as the distance between the rear plate and the faceplate is larger.
In order to prevent such a phenomenon, there is a method of forming an electrode for correcting the electron trajectory on the spacer (Japanese Patent Application Laid-Open (Kokai) No. 2000-235831), and a method of removing charges by causing some current to flow. Japanese Patent Application Laid-Open (Kokai) No. 57-118355 (1982) discloses a method of coating the surface of the spacer with tin oxide by applying a method of providing conductivity to the spacer.
Japanese Patent Application Laid-Open (Kokai) No. 3-49135 (1991) discloses a method of coating the spacer with a PdO-type glass material. Furthermore, destruction of the spacer due to insufficient connection or current concentration can be prevented by forming electrodes at connecting portions of the spacer with the faceplate and the rear plate of the spacer and applying an uniform electric field to the coated material.
By forming an electrode for correcting the electron trajectory on the spacer or forming a high-resistance film on the surface of the spacer as described above, it is possible to mitigate charging of the spacer and suppress attraction of electrons traveling near the spacer to the spacer.
In the above-described conventional methods, however, influence by charging of the spacer sometimes appears depending on the pitch between elements or driving conditions for the elements. For example, when the pitch between elements is small, influence by charging of the spacer appears because the spacer is close to electron emitting portions. Furthermore, for example, when driving conditions, such as the acceleration voltage and the driving voltage, change, the electric field around the spacer changes, resulting sometimes in incapability of removing charges even if a high-resistance film is formed on the spacer.